It is known that rotor blades for rotorcraft are manufactured predominantly from fiber composite material that, during operation of the rotorcraft, deflects in various directions and is thereby highly stressed. For that purpose, the rotor blade of a bearingless rotor encompasses at its inner end toward the rotor head a structural element configured in flexurally and torsionally flexible fashion, called a flex beam, that permits motions in the flapwise or lead-lag direction, as well as angular deflection about the torsion axis. The flex beam furthermore transfers the centrifugal forces of the blade to the rotor head. The torsionally flexible region of the flex beam is located inside a torsionally stiff control bag, by way of which control motions are introduced into the lift-generating blade region of the rotor blade. A rotor blade of this kind for a bearingless rotor is disclosed, for example, in DE 199 15 085 A1.